How To Understand The Structure Of Cell Membranes

Transcription

1 Chem Lecture 8 Lipids and Cell Membranes Like carbohydrates, lipids are one of the four major classes of biomolecules, which also include the proteins, carbohydrates and nucleic acids. Lipids are grouped not according to a chemical structure, as is the case for the other four classes, but rather they are grouped according to a physical property. Lipids comprise the molecules in a cell that can be extracted into non-polar solvents, which means they are non-polar, hydrophobic molecules. We will see that this does not mean that they do not contain hydrophilic functional groups, but all lipids molecules do contain large, hydrophobic regions. With cells being made up of largely water, this produces some very interesting and important cellular structure, not the least of which are the cell membranes.

2 Lipids are the components of a cell that can be extracted with organic solvents. 2

3 Lipids are the components of a cell that can be extracted with organic solvents. 2

4 Lipids are the components of a cell that can be extracted with organic solvents. Sterols 2

5 Lipids are the components of a cell that can be extracted with organic solvents. 3

6 Lipids Are the water-insoluble molecules found in a living cell. Roles for these molecules include Fuel fatty acids and ketone bodies Long term storage Triacylglycerides (fat) Messengers in signal transduction Steroids Diacylglycerol Components of membranes 4

7 Biological membranes define the boundary of a cell. Cellular communications with the surroundings are mediated by cell membrane Membranes are dynamics structures in which proteins float in a sea of lipids. 5

8 Biological membranes define the boundary of a cell. Cellular communications with the surroundings are mediated by cell membrane Membranes are dynamics structures in which proteins float in a sea of lipids. 5

9 Biological membranes define the boundary of a cell. Cellular communications with the surroundings are mediated by cell membrane Membranes are dynamics structures in which proteins float in a sea of lipids. 5

10 Membranes distinguish eukaryotic cells from prokaryotic cells. 6

11 Membranes play important roles. Energy Storage Information Transduction Compartmentalization Membranes are hydrophobic environments that separate two hydrophilic environments. 7

12 Regulation by Covalent Modification Protein Kinase A (PKA) is involved in the flight or fight response. This response is triggered by the release of the hormone epinephrine (adrenalin) by the adrenal glands. Chem 452, Lecture 6 - Regulatory Strategies 8

13 Features of membranes: They are sheet-like structures that form compartments. They are composed of lipids and proteins. Membrane lipids are amphipathic (both hydrophilic and hydrophobic) and form the sheetlike structure The proteins serve as the pumps, channels, receptors, energy transducers and enzymes. Membranes are non-covalent, fluid, asymmetric, assemblies Membranes are electrically polarized. 9

14 Features of membranes: They are sheet-like structures that form compartments. They are composed of lipids and proteins. Membrane lipids are amphipathic (both hydrophilic and hydrophobic) and form the sheetlike structure The proteins serve as the pumps, channels, receptors, energy transducers and enzymes. Membranes are non-covalent, fluid, asymmetric, assemblies Membranes are electrically polarized. 9

15 Features of membranes: They are sheet-like structures that form compartments. They are composed of lipids and proteins. Membrane lipids are amphipathic (both hydrophilic and hydrophobic) and form the sheetlike structure The proteins serve as the pumps, channels, receptors, energy transducers and enzymes. Membranes are non-covalent, fluid, asymmetric, assemblies Membranes are electrically polarized. 9

16 Fatty Acids Fatty acids are one of the major groups of lipids. 10

17 Fatty Acids Fatty acids are one of the major groups of lipids. 11

18 Fatty Acids Fatty acids are one of the major groups of lipids. 12

19 Fatty Acids Fatty acids are one of the major groups of lipids. 13

20 Fatty Acids 14

21 Fatty Acids Melting points are affected by chain length and the presense of cis double bonds. 15

22 Fatty Acids Melting points are affected by chain length and the presense of cis double bonds. 16

23 Next up Unit IV, Lecture 8 - Lipids and Cell Membranes, con d. (Chapter 12) 17